<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
             body{
                margin: 0;
                padding: 0;
            }
            .container{
                min-width: 400px;
                height: 200px;
                background-color: green;
                /*预留出位置*/
                padding: 0 200px;
            }
            .left, .right{
                width: 200px;
                height: 200px;
                background-color: red;
                float: left;
            }
            .main{
                width: 100%;
                height: 200px;
                background-color: blue;
                float: left;
            }
            .left{
                margin-left: -100%;
                position: relative;
                left: -200px;
            }
            .right{
                margin-left: -200px;
                position: relative;
                right: -200px;
            }


    </style>
</head>
<body>
    <header></header>
          <!-- 容器 -->
          <div class="container">
            <div class="main">中间栏</div>
            <div class="left">左边栏</div>
            <div class="right">右边栏</div>
        </div>
    <footer></footer>
</body>
</html>